Abrasive control valve

ABSTRACT

A flow valve for controlling magnetizable abrasive fed to a centrifugal wheel which includes a tubular valve member pivotally mounted for rocking movement between open and closed position and a magnet disposed adjacent the outlet end of the valve for buildup of magnetizable abrasive when in closed position.

This invention relates to valves for controlling the flow of abrasive inshot blasting equipment.

In the shot blasting industry, abrasive material, usually magnetizablemetal shot, flows from a hopper along a delivery tube to a rotatingthrowing wheel, which impels the abrasive against the article to becleaned. The flow of abrasive material is controlled by a valveassociated with the delivery tube. Such a valve consists of a platewhich can be swung across the delivery tube outlet to close same or toone side of the delivery tube to permit flow to the throwing wheel. Suchvalves allow the escape of noise from throwing wheels, of such intensityas to be detrimental to the hearing of the operatives, and it is anobject of the present invention to provide an improved control valve toreduce this hazard.

According to an aspect of the present invention there is provided avalve for use in controlling the flow of magnetizable abrasive from asupply to a throwing wheel via a delivery tube, the valve being whollyenclosed in a casing communicatingly connecting the delivery tube and ashroud of a throwing wheel.

According to another aspect of the present invention there is provided avalve for use in controlling the flow of magnetizable abrasive from asupply to a throwing wheel via a delivery tube, the valve comprising acasing or delivery tube, defining a flow-through aperture, a movablevalve member dimensioned such that, when it is in its valve-closingposition, there is a gap between the valve member and casing, andmagnetic means operable, when the valve member is in the valve-closingposition, to create a collar of magnetizable abrasive in the gap thus toclose the valve.

The control valve may comprise a casing with inlet and outlet apertures,disposed intermediate the ends of the delivery tube, a tubular valvemember pivotal about a horizontal axis in order to open or close thecontrol valve, abrasive-directing means from the inlet aperture into oneend of the valve member, and a magnet disposed in the casing adjacentthe other end of the valve member when the valve member is in thevalve-closing position.

Preferably, the magnet is a ring magnet.

Preferably, the abrasive directing means is a tube cooperating with theinlet aperture and projecting inwards of the casing into one end of thetubular valve member, the cross-sectional area of the tube being lessthan that of the tubular valve member.

Preferably, the casing is polygonal shaped with an aperture in a bottomwall, which aperture has an area of the same order to magnitude as saidother end of the valve member and in which a metallic ring is fitted,the ring magnet being tightly fitted inside the metallic ring, and aplate covering the metal ring and ring magnet on the outside of thecasing.

Preferably, the plate can be removed and a tube fitted to the casingaround the aperture through which tube abrasive can be passed tore-cycling means.

Preferably, the tubular valve member is frusto-conical in shape.

Alternatively, the control valve may comprise a magnetic or magnetizablevalve member pivotal between a valve-closing position across thedelivery tube interior to a valve-opening position alongside thedelivery tube, which valve member is of lesser cross-sectional area thanthat of the delivery tube but which magnetically attracts a collar ofabrasive to effect with the valve member closure of the delivery tube.

The delivery tube preferably has a lateral housing for accommodating thevalve member when the latter is in its valve opening position.

The top surface of the valve member is preferably lipped so that a layerof abrasive is created across said surface thus assisting in resistingwear.

More specifically, the valve member comprises a magnetic platesandwiched between two larger plates, all of similar cross-sectionalshape to that the delivery tube the bottom plate being larger in areathan the top plate and having a slightly smaller cross-sectional areathan the delivery tube so that a conical collar of abrasive is formed inthe gap between the periphery of the valve member and the tube wall.

Means is preferably provided for pivotting the valve member betweenhorizontal (valve closed) and vertical (valve opened) positions.

Embodiments of the present invention will now be described by way ofexample with reference to and as shown in the accompanying drawings, inwhich:

FIG. 1 is a front sectional view of a first embodiment of control valveaccording to the invention; and

FIG. 2 is a side sectional view of the control valve.

The control valve FIGS. 1 and 2 comprises a polygonal-shaped cast ironcasing 10 in which there is an inlet provided at the top to allow thepassage of magnetizable abrasive along a vertical tube 11, which isattached to the outside of the casing 10, from a supply. There isanother tube 12, of smaller cross-sectional area than that of the tube11, which projects inwardly of the casing 10 at an angle to the tube 11into a hollow bucket-shaped valve member 13. The valve member 13 isfixedly mounted on two horizontal shafts 14, which shafts 14 arerotatably mounted in two rubber/metal sandwich bushes 15 in the casing10, which bushes prevent wear and binding to dust from the metallicabrasive, and reduce friction.

There is provided a large aperture 16 in one of the walls of the casing10 in which there is fitted an annular metal ring 17 of the samecross-sectional area as the aperture 16. An annular ring magnet 18 isfitted inside the metal ring 17, the outside diameter of the ring magnet18 being equal to the inside diameter of the metal ring 17. The ringmagnet 18 may either be a permanent magnet or an electromagnet. Theaperture 16, metal ring 17 and ring magnet 18 are all covered by a plate19 positioned on the outside of the casing.

There is an outlet 20 provided in the base of the casing 10 which outletcooperates with a delivery tube 21 attached to the base of the casing10. The delivery tube 21 is connected at its other end to the center ofa shroud 22 of a vertically disposed centrifugal throwing wheel.

In use, metallic abrasive is passed down the vertical tube 11 under theforce of gravity into the tube 12. Then, if the valve member 13 is inthe open position, (broken lines) 23, the abrasive flows through thehollow valve member 13, through the delivery tube 21 and then into theshroud 22. In order to close the valve, the valve member 13 is rotatedvia the shafts 14 to the closed position (solid lines) 24 by any kind ofmotive power or manually. At the same time, the magnet 18, if anelectromagnet, is switched on by an operative. In this position 24, acollar of metallic abrasive is formed between the bottom of the valvemember 13 and the metal ring 17 and ring magnet 18 preventing anyabrasive dropping down the delivery tube 21 to the throwing wheel.

The control valve can be used as a directional valve instead of anopen/close valve if required. In this case the plate 19 is removed and atube 25 leading to re-cycling means is attached to the casing 10 outsideof the aperture 16. The metallic abrasive can therefore either pass downthe delivery tube 21 to the shroud 22 if the valve member 13 is inposition 23, or down tube 25 to re-cycling means, in which it issupercleaned, if the valve member is in position 24.

The control valve has fail-safe means associated with it (not shown)which acts, in the event of a power failure, on the valve member 13 soas to rotate it from the open position 23 to the closed or re-cycledposition 24. The shroud 22 and delivery tube 21 are therefore preventedfrom being blocked with abrasive. The fail-safe means may, for example,be a spring. Rubber/metal sandwich bushes 15 also help to move the valvemember from position 23 to 24 since there is a natural elasticityassociated with them.

The main advantage of this control valve is that the movement of thevalve member from the open to the closed position is much easier than inknown valves since the column of shot in the valve member is moved also.In known metallic abrasive control valves, it is necessary to push asidelarge quantities of abrasive in order to close the valve.

The control valve according to the invention is also easier to closebecause there is a gap between the bottom of the valve member 13 and themetal ring 17 and ring magnet 18 which is filled by a collar of metallicabrasive as hereinbefore described. Known valves, in their closedposition, are a tight fit between the valve member and the casing. Thus,they are difficult to close.

I claim:
 1. A valve for use in controlling the flow of magnetizableabrasive from a supply to a throwing wheel via a delivery tube, thecontrol valve comprising a casing, with inlet and outlet apertures,disposed intermediate the ends of the delivery tube, a tubular valvemember pivotal about a horizontal axis in order to open or close thecontrol valve, abrasive directing means from the inlet aperture into oneend of the valve member and a magnet disposed in the casing adjacent theother end of the valve member when the valve member is in the closedposition.
 2. A valve as claimed in claim 1, in which the magnet is aring magnet.
 3. A valve as claimed in claim 1, in which the abrasivedirecting means is a tube cooperating with the inlet aperture andprojecting inwards of the casing into one end of the tubular valvemember, the cross-sectional area of the tube being less than that of thetubular valve member.
 4. A valve as claimed in claim 2, in which thecasing is polygonal shaped with an aperture in a bottom wall, whichaperture has an area of the same order of magnitude as said other end ofthe valve member and in which a metallic ring is fitted, the ring magnetbeing tightly fitted inside the metallic ring, and a plate covering themetal ring and ring magnet on the outside of the casing.
 5. A valve asclaimed in claim 4, in which the plate can be removed and a tube fittedto the casing around the aperture through which tube abrasive can bepassed to re-cycling means.
 6. A valve as claimed in claim 1, in whichthe tubular valve member is frusto-conical in shape.